Large diesel powered trucks and other vehicles often include multiple fuel tank systems that employ two or more fuel tanks. It is generally undesirable for air to be drawn into the truck engine of either a single or multiple fuel tank system. This is particularly so when operating a diesel engine since air in the diesel engine can create considerable difficulty for the operator to seal the air leak and re-initiate suction of flow of fuel to the diesel engine. If the engine on a large truck, such as a tractor-trailer truck, for example, is deprived of fuel while under way, it will stop the engine and damage the fuel pump. Most commonly, air is drawn into the fuel tank system as a result of depletion of the liquid fuel in the fuel tanks. Accordingly, it is desirable to provide apparatus to prevent introduction of air into the fuel line of a fuel tank system.
Still further, with multiple fuel tanks, it is desirable to use as much fuel from both tanks as possible, thereby to maximize the benefit of providing multiple fuel tanks. However, for a variety of reasons the fuel level in the two tanks may not be equal and, therefore, it may be possible to draw air into the fuel line as a result of one tank being depleted of fuel while the other tank still has a substantial amount of fuel. Accordingly, it is particularly advantageous to provide a system for preventing the introduction of air into the fuel line of a multiple fuel tank system.
One prior art fuel transfer system attempts to maintain the fuel levels in both tanks substantially constant, so that the maximum amount of fuel can be drawn from both tanks without drawing air into the engine. The fuel transfer system usually includes crossover lines coupled to the bottom walls of the tanks. Since the fuel flow between tanks depends on gravity, the crossover lines are typically the lowest point on the fuel tanks.
However, since these crossover lines are generally the lowest parts of the vehicle, they are susceptible to accidental breakage due to debris on the highway or other obstructions that may impact against the below-tank crossover line. Breakage in a fuel tank results not only in accidental loss of the liquid fuel contained in the fuel tank but also represents a safety and environmental hazard. Accordingly, multiple fuel tank systems of this type are undesirable.